I am wondering if this answer could apply to your case as well. I imagine you have quite a number of lights in your level: https://answers.unrealengine.com/questions/563103/editor-vs-build-performance.html
I am wondering if this answer could apply to your case as well. I imagine you have quite a number of lights in your level: https://answers.unrealengine.com/questions/563103/editor-vs-build-performance.html